This project will use developmental patterns of early emotional functioning and communication to predict social, behavioral, and cognitive functioning in the second and third year of life. Contrasts between 100 typically developing infant siblings and 100 infant siblings of children with Autism Spectrum Disorder (ASD) - who are at risk for a range of disruptions of emotion, communication, and cognition - will illuminate these developmental processes from a developmental psychopathology perspective. In the first year of life, associations between temperamental (Lab-TAB) and communicative (face-to-face/still-face) assessments of positive and negative emotion, cerebral indices of approach motivation (EEG laterality), and the development of communicative intentionality (infant joint attention) will be determined. These constructs will be used to predict a set of developmental^ linked processes including dyadic relationship quality, parent rated behavioral difficulties and strengths, standardized measures of linguistic and cognitive functioning, and ASD- related symptomatology in the second and third year of life. Relationship quality is a central construct, encompassing security of attachment, parental warmth and control, and child cooperation and warmeth in a range of social situations. Relationship quality is expected to mediate pathways to all outcomes with the exception of ASD symptomatology. Children with high levels of ASD symptomatology are expected to show deficits in both early measures emotional communication and later measures of social, communicative, and cognitive functioning. ASD symptomatology is expected to be directly related to early emotional functioning. This proposal utilizes multi-method assessment of emotional functioning early in infancy to confront the task of predicting intentional communication and later indices of healthy interaction, and competent linguistic and cognitive functioning. The models tested will shed specific light on the prediction and prevention of health- related outcomes including behavior problems, poor relationship quality, and ASD symptomatology in an at- risk and typically developing sample. Examination of predictive associations in typically developing infants and infant siblings of children with ASD will shed light on pathways to healthy development, psychopathologic deviations from those pathways, and potential intervention strategies for infants at risk for developmental difficulties.